Abstract:

The invention concerns a process for producing a thin layer solar cell
module with a plurality of segments that are electrically connected in
series and arranged on a common substrate. The invention additionally
concerns the corresponding thin layer solar cell modules and a production
line that is suitable for conducting the production process. The process
has steps for application of layers onto the substrate to form at least
one electrode and one photoactive layer sequence and has steps for
structuring the applied and/or to be applied layers to form the plurality
of segments. At least one electrode and one photoactive layer sequence
are applied before structuring steps are carried out.

Claims:

1. A process for producing a thin layer solar cell module with a plurality
of segments that are electrically connected in series and arranged on a
common substrate, with the process comprising:applying layers to the
substrate to form at least one electrode and one photoactive layer
sequence;structuring the applied and/or to be applied layers to form the
plurality of segments,wherein the at least one electrode and the one
photoactive layer sequence are applied before the structuring is carried
out.

2. The process according to claim 1, wherein forming an electrode
comprises applying at least one layer of a transparent conductive oxide
and/or a metal layer.

3. The process according to claim 1, wherein forming the one photoactive
layer sequence comprises applying at least one individual layer of
amorphous or microcrystalline Si and/or amorphous or microcrystalline
SiGe and/or a compound semiconductor.

4. The process according to claim 3, wherein forming the one photoactive
layer sequence comprises applying a p-doped, an intrinsic and an n-doped
layer of amorphous Si and/or a p-doped, an intrinsic and an n-doped layer
of microcrystalline Si and/or a p-doped, an intrinsic or an n-doped layer
of amorphous Si(Ge).

5. The process according to claim 1, wherein applying the layers comprises
performing a PVD process, and/or a CVD process.

6. The process according to claim 1, wherein the substrate comprises
glass.

7. The process according to claim 1, wherein a structuring of already
applied layers comprises creating a separating line by laser radiation
and/or by mechanical scoring and/or by selective etching.

8. The process according to claim 7, wherein laser light is directed so
that one or more layers are locally removed.

9. The process according to claim 7, wherein laser light is directed so
that one or more layers are locally heated so that a physical property of
at least one of the layers is changed.

10. The process according to claim 1, wherein structuring of already
applied layers comprises creating a contact line by laser radiation.

11. The process according to claim 10, wherein laser light is directed so
that overlying layers of different materials become locally heated and a
material compound is formed that has physical properties that differ from
original materials.

12. The process according to claim 11, wherein a melt of the different
materials is locally formed and in which the material compound results
from the melt.

13. The process according to claim 7, wherein an isolating line is created
from an electrically isolating material within the separating line.

14. The process according to claim 13, wherein the isolating line is
applied by an ink jet printing process.

15. The process according to claim 1, wherein structuring of subsequently
to be applied layers takes place by means of a cover line made of a
soluble material.

16. The process according to claim 15, wherein the cover line is applied
by an ink jet printing process.

17. A thin layer solar cell module with a plurality of segments that are
electrically connected in series, which is produced by a process
according to claim 1.

18. A thin layer solar cell module with a plurality of segments that are
electrically connected in series, wherein an isolating line of isolating
material is applied in a region of a separating line, which interrupts a
first electrode of the thin layer solar cell module to form the segments
and which is covered by a second electrode.

19. The thin layer solar cell module according to claim 18, wherein the
isolating line contains an isolating polymer.

20. A thin layer solar cell module with a plurality of segments that are
electrically connected in series, wherein one electrode of an
electrically conductive oxide is electrically interrupted by a separating
line, the one electrode having locally different physical properties in a
region of the separating line than outside of the separating line.

21. The thin layer solar cell module according to claim 20, wherein the
locally different physical properties in the region of the separating
line derive from a change of doping after recrystallization of the one
electrode in the region of the separating line.

22. The thin layer solar cell module according to claim 20, wherein the
locally different physical properties in the region of the separating
line derive from formation of an oxide of an element from a photoactive
layer sequence that is adjacent to the one electrode in the region of the
separating line.

24. A thin layer solar cell module with a plurality of segments that are
electrically connected in series, the thin layer solar cell module
comprising:a first electrode;a photoactive layer sequence;a second
electrode; anda contact line, the second electrode being electrically
connected to the first electrode via the contact line for series
connection of the segments, wherein the contact line, in a region of the
photoactive layer sequence, contains a conductive material compound
and/or a conductive alloy of elements of the photoactive layer sequence
and the second electrode.

25. The thin layer solar cell module according to claim 24, wherein the
photoactive layer sequence contains Si and wherein the contact line
contains a silicide.

26. A thin layer solar cell module with a plurality of segments that are
electrically connected in sequence, wherein an electrically conductive
adhesive strip or a strand of a conductive paste is applied in a region
of a separating line that interrupts a first electrode of the thin layer
solar cell module to form the segments and a second electrode, to restore
the electrical connection to the second electrode.

27. A production line for production of a thin layer solar cell module on
a glass substrate and configured to run a process according to claim 1,
the production line comprising: a coating device with a first vacuum
lock, at least two coating stations and a second vacuum lock and is
designed so that the glass substrate, after being loaded into the coating
device, can pass through the first vacuum lock, at least two coating
stations in succession under vacuum conditions before the glass substrate
is unloaded through the second vacuum lock from the coating device.

28. The production line according to claim 27, wherein PECVD coating
stations and/or PVD/(LP)CVD coating stations are provided in the coating
device.

29. The production line according to claim 27, further comprising a
cleaning station directly coupled to the first vacuum lock.

30. The production line according to claim 27, further comprising a linear
roller drive provided as a transport system through the coating device.

31. The production line according to claim 27, comprising a structuring
device, in which, on a movable process head, at least two different
structuring tools are made available for structuring at least one layer
of the thin layer solar cell module.

32. The production line according to claim 31, wherein the movable process
head is equipped to make available laser radiation simultaneously at
least two different wavelengths.

33. The production line according to claim 31, wherein the movable process
head is equipped to make available laser radiation and has an ink jet
printing device.

34. The production line according to claim 31, wherein the movable process
head is equipped to lay an adhesive band on the thin layer solar cell
module.

Description:

[0001]This application is a continuation of co-pending International
Application No. PCT/EP2008/058864, filed Jul. 8, 2008, which designated
the United States and was not published in English, and which claims
priority to German Application No. 10 2007 032 283.8 filed Jul. 11, 2007,
both of which applications are incorporated herein by reference.

TECHNICAL FIELD

[0002]Embodiments of the invention concern a method for producing a thin
layer solar cell module with a plurality of electrically series-connected
segments arranged on a common substrate. Other embodiments concern the
corresponding thin layer solar cell modules and a production line that is
suitable for conducting the production process.

BACKGROUND

[0003]Thin layer solar cell modules, also called thin layer photovoltaic
modules, have photoactive layers with thicknesses in the range of
micrometers. The semiconductor material that is used in the photoactive
layer or layers can be amorphous or microcrystalline. A combination of
layers of amorphous and microcrystalline semiconductor material within a
cell is also possible, for example, with the so-called tandem cells and
the so-called triple cells. Possibilities for semiconductor materials are
Se and Gi and compound semiconductors like CdTe or Cu(In, Ga)Se2
(abbreviated CIS or CIGS). In spite of a somewhat lower efficiency than
layer solar cell modules, because of their clearly lower material
requirements, thin layer solar cell modules represent an economical and
technically relevant alternative to solar cell modules that are produced
on the basis of single-crystal or polycrystalline semiconductor layers of
macroscopic thicknesses.

[0004]To be able to use economic modules with a surface area that is as
high as possible, without the current laterally discharged in the
electrodes of the solar cells becoming so great that high ohmic losses
arise, thin layer solar cell modules are usually divided into a plurality
of segments. The strip shaped segments, which as a rule are a few
millimeters to centimeters wide, mostly run parallel to one edge of the
module. The segments formed in that individual layer of the layer
structure of the solar cell are interrupted by thin separating lines with
a continuous substrate. The separating lines lead, for one thing, to like
layers of adjacent segments being electrically isolated from each other
and, for another, to the fact that subsequently applied layers can be
electrically connected to underlying layers along a contact line. With
the appropriate arrangement of the separating lines a serial connection
of the individual segments can in this way be achieved.

[0005]According to the prior art the formation of a separating line takes
place in each case immediately after application of the layer. Since the
application of layers usually takes place under vacuum conditions, but
the formation of the separating lines usually takes place spatially
separately under atmospheric conditions, the production process according
to the prior art requires a complicated process setup. In addition, with
the frequent loading and unloading operations in and out of the vacuum
there is the danger of incorporating contaminants between the layers of a
solar cell. Material removed during the structure-producing operations
that settles on the layers can also be such a contaminant.

SUMMARY

[0006]In one aspect, the invention provides a method for producing a thin
layer solar cell module that allows a simpler and more efficient conduct
of the process. In other aspects the invention specifies a thin layer
solar cell module that can be produced in such a process and to create a
production line for producing such a thin layer solar cell module.

[0007]According to a first aspect of the invention the task is solved by a
method for producing a thin layer solar cell module with a plurality of
segments that are arranged on a common substrate and electrically
connected in series, where the process includes steps for application of
layers onto the substrate to form at least one electrode and one
photoactive layer sequence and steps for structuring the applied and/or
to be applied layers in order to form the plurality of segments. At least
one electrode and one photoactive layer sequence are applied before
structuring steps are carried out.

[0008]Therefore, initially a group of at least two processes for
deposition of layers is carried out before structuring steps for
segmentation are carried out. The combining of process steps that are
each carried out under comparable conditions (for example, vacuum versus
atmospheric conditions) facilitates the conduct of the process and is
suitable for reducing the incorporation of contaminants between the
layers in the case of thin layer solar cell modules.

[0009]In an advantageous embodiment of the process the structuring of
already applied layers takes place by creating a separating line by means
of a laser beam and/or by mechanical scoring and/or selective etching.
Especially preferably, laser radiation is directed so that one or more
layers are locally removed or that one or more layers are locally heated
so that the physical properties of at least one of the layers, in
particular, its conductivity, is changed.

[0010]In another advantageous embodiment of the process the structuring of
already applied layers takes place by creating a contact line through
laser radiation. Especially preferably, laser radiation is directed so
that layers of different material lying one on the other are locally
heated and a material compound that has physical properties that differ
from the original materials and, in particular, is conductive is formed.

[0011]In another advantageous embodiment of the process an isolating line
of an electrically isolating material is created within one of the
separating lines. Especially preferably, the isolating line is applied by
an ink jet printing process.

[0012]According to another advantageous embodiment of the process a
structuring of layers to be brought together subsequently takes place
with the help of a cover line of a soluble material. Especially
preferably, the cover line is applied by an ink jet printing process.

[0013]The advantageous embodiments of the process according to the first
aspect of the invention specifies structuring measures that are suitable
for conducting a structuring of a (single) layer even within a layer
stack having at least two layers applied one on the other. They are
therefore ideal structuring measures for the method in accordance with
this application.

[0014]According to a second aspect of the invention the task is solved by
a thin layer solar cell module with a plurality of segments that are
electrically connected in series that is produced by a method as
described herein.

[0015]According to a third aspect of the invention the task is solved by a
thin layer solar cell module with a plurality of segments that are
electrically connected in series, in which an isolating line of an
isolating material is applied in the region of a separating line, which
interrupts a first electrode of the thin layer solar cell module for the
formation of the segments which is covered with a second electrode.
Preferably, the isolating line contains an isolating polymer.

[0016]According to a fourth aspect of the invention the task is solved by
a thin layer solar cell module with a plurality of segments electrically
connected in series, in which an electrode of an electrically conductive
oxide that is turned toward the substrate is electrically interrupted by
a separating line, where the electrode locally in the region of the
separating line has different physical properties than outside the
separating line.

[0017]Preferably, the locally different physical properties in the region
of the separating line derive from a change of doping after
recrystallization of the electrode in the region of the separating line
or formation of an oxide of an element from a photoactive layer sequence
adjacent to the electrode in the region of the separating line.
Especially preferably, the photoactive layer sequence contains Si and the
separating line contains Si oxide.

[0018]According to a fifth aspect of the invention the task is solved by a
thin layer solar cell module with a plurality of segments electrically
connected in series including a first electrode, a photoactive layer
sequence and a second electrode, in which there is a contact line via
which the second electrode is electrically connected to the first
electrode for series connection of the segments, where the contact line
contains, in the region of the photoactive layer sequence, a conductive
material compound and/or a conductive alloy of elements of the
photoactive layer sequence and the second electrode. Preferably, the
photoactive layer sequence contains Si and the contact line contains a
silicide.

[0019]According to a sixth aspect of the invention the task is solved by a
thin layer solar cell module with a plurality of segments electrically
connected in series, in which an electrically conductive adhesive strip
or a strand of a conductive paste is applied in the region of a
separating line that interrupts a first electrode of the thin layer solar
cell module for formation of the segments, and a second electrode for
restoration of the electrical connection to the second electrode.

[0020]In the thin layer solar cell modules in accordance with the second
through sixth aspects of the invention, the different layers (electrodes
and photoactive layer sequence) are structured so that a series
connection can be created after at least two layers have already been
applied. The combining of the process steps for application of the layers
results in lesser contamination, in the thin layer solar cell modules,
for example, due to frequent loading and unloading processes, and thus it
results in better layer quality, from which higher efficiency of the
cells results. Moreover, in the case of these thin layer solar cell
modules the process steps for structuring of the layers can be combined,
which leads to better positioning of the structuring steps in the
different layers with respect to each other. This results in a small
contact area for the series connection and consequently a higher surface
area yield on the part of the cells.

[0021]According to a seventh aspect of the invention the task is solved by
a production line for producing a thin layer solar cell module on a glass
substrate, in which, with a coating plant that has a first vacuum lock,
at least two coating stations and a second vacuum lock and is designed so
that the glass substrate, after being loaded into the coating plant
through the first vacuum lock can pass through the minimum of two coating
stations in a succession under vacuum conditions, before the substrate is
discharged from the coating plant through the second vacuum lock.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]The invention will be explained in more detail by means of
embodiment examples using five figures.

[0023]FIG. 1 shows a schematic representation of a layer structure of a
thin layer solar cell module according to the prior art;

[0024]FIGS. 2a-4f show schematic representations of the layer structure of
thin layer solar cell modules, each for different process stages in a
process in accordance with the application; and

[0025]FIG. 5 shows a plant for production of thin layer solar cell
modules.

[0061]FIG. 1 shows the layer structure of a thin layer solar cell module
according to the prior art in a schematic representation. A first
electrode 2, a photoactive layer sequence 3 and a second electrode 4 are
applied to a substrate 1. The first electrode 2, the photoactive layer
sequence 3 and the second electrode 4 are laterally interrupted by
separating lines 10, 11 and 12. The three separating lines 10, 11 and 12
are in turn laterally spaced apart and divide the represented segment of
the thin layer solar cell module into a first segment 5 to the left of
separating line 10, a second segment 7 to the right of separating line 12
and a contact region 6 lying between them.

[0063]Amorphous or microcrystalline semiconductors of group IV, for
example, a-Si, a-SiGe, μC--Si, or compound semiconductors such as CdTe
or Cu(In, Ga)Se2 (abbreviated CIS or CIGS) can be used as the active
semiconductor material for the photoactive layer sequence 3. Layers of
materials different from those indicated above can also be combined in
the photoactive layer sequence 3. In addition, partially reflecting
layers (intermediate reflectors) of a conductive oxide and/or a
conductive semiconductor layer can be present in the photoactive layer
sequence 3.

[0064]The photoactive layer sequence 3 typically includes at least one p-
and one n-doped semiconductor layer, i.e., a diode junction. In the case
of thin layer solar cells based on silicon, the p- and the n-doped layers
are usually additionally separated by an extended intrinsic layer
(i-layer). For better utilization of the wavelength spectrum a number of
pin-layer stacks with different absorption spectra can be provided one on
top of the other. The Si tandem cell preferably has a pin-layer stack of
a-Si and a pin-layer stack of μC--Si and in the Si triple cell there
is additionally a pin-layer stack of a-Si(Ge). In this connection it is
expressly pointed out that within the scope of this application the
photoactive layer sequence 3 is not limited to a pin- or nip-layer stack
(diode junction), but includes multiple stacks like those of tandem or
triple cells.

[0065]Typically the p-doped layer is turned toward the sun. With reference
to the production process, a differentiation is made between the
so-called pin-cells and nip-cells depending on the sequence in which the
differently doped layers of the photoactive layer sequence 3 are applied.
In the case of pin-cells the (growth) substrate 1 is transparent and in
the end module also forms the carrier substrate that is turned toward the
sun. Typically (sheet) glass is used for this. In the case of nip-cells,
glass or even a (metal) film can be used as growth substrate. The carrier
substrate, through which sunlight passes in operation, is not laminated
onto the module until the end of the production process. The nip-layer
stack remains bonded to the growth substrate.

[0066]All of the embodiment examples that are presented show pin-cells.
This is purely a matter of example and does not represent any limitation.
All of the processes described within the scope of this application can
be used both in the case of pin-cells and nip-cells.

[0067]In the example of a pin-cell shown in FIG. 1 the first electrode 2,
which is turned toward the sun and which in what follows is also called
the front side electrode, is usually formed of transparent conductive
oxides (TCO), for example, SnO2 or ZnO or ITO (indium tin oxide). The
second electrode 4, which is turned away from the sun and is also called
the back side electrode in what follows, can likewise have a TCO layer or
also can be formed by metals like Ag, Al, Mo, or from a combination of
TCO and a metal layer.

[0068]If the process described in the application is extended to nip cells
one should note that the function of electrodes 2 and 4 is
correspondingly reversed. The first electrode 2, which is applied first,
can in the case of a nip cell include a metal layer and be the back side
electrode turned away from the sun in operation. Correspondingly, the
last applied second electrode 4 is made transparent and forms the front
side electrode turned toward the sun.

[0069]In the process of producing the thin layer solar cell modules
according to the prior art that is shown in FIG. 1 the front side
electrode 2, for example, TCO, is applied to the substrate 1, for example
glass, first. Then the separating line 10 is produced in the front side
electrode 2 by laser light of an appropriate wavelength, for example,
1064 nm, or by mechanical scoring or by selective etching. This
separating line 10 runs over the entire width of the module (in the
figure perpendicular to the plane of the paper). The laser light can be
directed both through substrate 1 and also from the layer side. The
separating line 10 separates electrodes 2 over their entire thickness to
a width of 5-1000 μm, with typical widths lying in the range of 10-50
μm. After structuring of the front side electrode 2 is complete, the
photoactive layer sequence 3 is applied and then structured by generating
the separating line 11. Separating line 11 in photoactive layer sequence
3 is usually generated by laser light at a wavelength of 532 nm if Si is
used as the photoactive material. Finally, the back side electrode 4 is
applied; it comes into direct contact with the front side electrode 2 in
the region of separating line 11. The separating line 12 is generated in
a last step in order to separate the back side electrode 4 of the first
segment 5 electrically from the back side electrode 4 of the second
segment 7. It is conventional here to direct laser light through the
substrate 1 at a wavelength that is not absorbed by the front side
electrode 2, but is absorbed by the photoactive layer sequence 3, thus
again 532 nm, for example, so that the photoactive layer sequence 3
evaporates, and the metal back side electrode 4 can melt and be
jettisoned in the region of separating line 12 or even can in turn
evaporate. The alternating steps for application of the layers and for
structuring the layers lead to a series connection of the two segments 5
and 7 as is evident by the arrow symbolizing the flow of current in FIG.
1.

[0070]From the standpoint of process technology there is the problem that
steps for layer deposition that take place in a vacuum alternate with
structuring steps, for the formation of separating lines 10, 11 and 12,
which take place under atmospheric conditions (ambient air or even a
protective gas atmosphere) and in an entirely different process station.
Besides the elevated expenditure in the conduct of the process, the
correspondingly frequently necessary loading and unloading operations
carry the danger that contaminants will be deposited between the layers.

[0071]In addition, with thin layer solar cells it is desirable to make the
contact region 6 as narrow as possible, since it is an inactive area,
which reduces the surface area yield of the solar cell module. The
separate structuring processes, between which the substrate moreover is
sent to other process chambers to apply the layers, necessarily leads to
a lack of precision in positioning the separating lines 10, 11 and 12
with respect to each other. As a consequence the spacing of separating
lines 10, 11 and 12 from each other must a priori be chosen to be so wide
that the unavoidable positioning error will be harmless for the correct
conduct of the series connection of the segments.

[0072]FIG. 2 illustrates a first embodiment example of a process in
accordance with the invention for producing a thin layer solar cell
module.

[0073]As FIG. 2a shows, first a first electrode 2 and a photoactive layer
sequence 3 are applied to a substrate 1. As an example, substrate 1 is
sheet glass, the first electrode 2 is a front side electrode of TCO and
the photoactive layer sequence 3 is a sequence of p-doped, intrinsic and
n-doped amorphous or microcrystalline silicon. The front side electrode 2
and the photoactive layer sequence 3 can be applied in successive vacuum
coating processes without having to remove substrate 1 from the vacuum
for this. It is also possible to start with a substrate 1 that has
already been provided with a TCO layer as front side electrode 2. In this
case only the photoactive layer sequence 3 needs to be applied.

[0074]After removing substrate 1 from the vacuum there follows a first
structuring step, in which the photoactive layer sequence 3, for the
formation of a separating line 20, is interrupted to a width of >100
μm and typically 150 μm. This can take place, for example, by
introducing laser radiation at a wavelength of 532 nm either from the
layer side or through the substrate 1. The resulting layer structure is
schematically shown in FIG. 2b.

[0075]Then an additional separating line 21 is produced within the region
of separating line 20; it interrupts the front side electrode 2 on a
width of typically 10-40 μm (see FIG. 2c). Laser radiation at a
wavelength of 1046 nm or 355 nm is suitable for formation of the
separating line 21. It is advantageous for the separating line 21 not to
be centrally positioned with respect to separating line 20, but rather to
be offset in the left hand region of separating line 20, so that the left
edges of separating line 20 and 21 are laterally spaced from each other
about 20-30 μm. Like separating line 20, separating line 21 can be
generated by means of laser radiation, which is directed from the layer
side or from the substrate side.

[0076]Here it is preferred that the laser radiation needed to form
separating lines 20 and 21 be provided from a single process head, which
moves over substrate 1, so that positioning of the two separating lines
20 and 21 with respect to each other that is as precise as possible and
constant over the entire length of the separating lines is guaranteed.

[0077]Then, as shown in FIG. 2d, an isolating line 22, like an
electrically isolating strand, is applied along the separating line 21.
Advantageously, the isolating line 22 fills separating line 21 and
projects about 20-30 μm on both sides into separating line 20, so that
the left edge of separating line 20 becomes isolated and passivated.
However it is important that a sufficient region of the front side
electrode 2 in separating line 20, typically 20-50 μm wide, is not
covered by isolating line 22. The height of the isolating line 22 can
typically be 5-50 μm.

[0078]An ink jet printing process is especially suitable for application
of the isolating line 22. An electrically isolating polymer that hardens
after application can be used as the isolating material.

[0079]The height to width ratio of isolating line 22 can be determined
both by the technique of application of the isolating material and its
flow properties. Preferably a surface that is free of edges and cross
sections that run perpendicular to the substrate should preferably be
formed, so that it can then be readily covered over by the subsequently
applied back side contact 4. In FIG. 2d, for example, a rather high round
profile is shown and, as an alternative, a flat profile of isolating line
22 is shown as a dotted line.

[0080]In addition, in a region to the right of separating line 20 on the
photoactive layer sequence 3, a cover line 23 of a soluble lacquer is
likewise applied in strand form over the entire width of substrate 1
(FIG. 2e). Again an ink jet printing process is suggested for this. A
profile that is as box shaped as possible is advantageous for cover line
23, as is shown in idealized form in FIG. 2e. The width of cover line 23
is typically 50 μm and the distance of the line to the right edge of
separating line 20 should be about 20-50 μm. The height of cover line
23 is not critical, but it should be greater than the thickness of the
back side electrode 4, which is still to be applied. It is advantageous
to apply both the isolating line 22 and the cover line 23 with the same
process head from the layer side. It is also conceivable that all of the
structuring steps, thus the radiation with laser light to form separating
lines 20 and 21 and the application of isolating line 22 and cover line
23, take place from a single process head, which operates from the layer
side. In this way the relative positioning of all of the structuring
elements with respect to each other is ensured as well as possible. If
the isolating line 22 and cover line 23 are applied by a separate process
head after laser structuring, this second process head can be connected
to an optical detection system through which the position of the process
head is tracked from the detected position of separating lines 20 or 21.

[0081]As shown in FIG. 2f, this is followed by the application of the back
side electrode 4, for example a ZnO layer, followed by an Ag and/or Al
layer in a vacuum deposition process or possibly in a spray coating
process. The different profiles of the isolating line 22 on the one hand
and the cover line 23 on the other lead to the isolating line 22 being
covered over by a continuous layer, whereas the sides of the cover line
23 are not or are only incompletely covered over by the back side
electrode 4.

[0082]Then the soluble varnish of cover line 23 is removed by a suitable
solvent, so that the separating line 24 remains in the back side
electrode 4. The application of the cover line 23 to this extent is a
structuring process for a still to be applied layer (in this case the
back side electrode 4).

[0083]The process results in the thin layer solar cell module shown in
FIG. 2g. The resulting segmentation into a first segment 5 on the left, a
second segment 7 on the right and the contact region 6 lying between them
is shown in the schematic representation. In addition, arrows symbolizing
the flow of current illustrate the series connection of segments 5 and 7
that has taken place.

[0084]The thin layer solar cell module is characterized by the isolating
line 22 that is covered over by the back side electrode 4 and completely
enclosed by it. The typical dimensions and spacings of the structuring
elements indicated in the previous description can lead to a width of the
contact region that is less than 200 μm, which results in efficient
utilization of the area of the thin layer solar cell module.

[0085]FIG. 2h shows an alternative embodiment of the thin layer solar cell
module. In this embodiment the separating line 20 was not made over the
entire width indicated in connection with FIG. 2b. Rather, a narrower
separating line 25 was formed, in which the separating line 21 in this
case was made centrally positioned and an additional separating line 26
was formed. This division into two separating lines that interrupt the
photoactive layer sequence 3 can be advantageous from the standpoint of
process technology, since all in all a lesser width must be removed and
correspondingly a lower laser power is required.

[0086]An advantage of the process shown in FIG. 2 is that two layers or
layer sequences (see FIG. 2a) are applied before a first structuring step
is carried out. The number of transfers between different process
stations and the number of loading and unloading operations into the
vacuum that is necessary for application of the layers can be kept low.
In addition, all of the structuring steps can be carried out grouped in
succession in one process station, so that a reorientation of the
substrate 1 before each structuring step is no longer necessary.
Optionally it is even possible to carry out all of the structuring steps
quasi-simultaneously using one process head. To increase throughput in
structuring, moreover, a number of these process heads can be used
parallel and side by side to process the contact regions between
different segments. These process heads can be outfitted with separate
lasers or can be supplied by separate lasers, or can be supplied from a
common laser whose light is sent to the different process heads by beam
splitters.

[0087]In a manner analogous to FIG. 2, FIG. 3 shows another example of an
embodiment of a process in accordance with the application. The
statements about possible materials made in connection with FIG. 2 can be
extended to this embodiment example.

[0088]As FIG. 3a shows, in this case the front side electrode 2, the
photoactive layer sequence 3 and the back side electrode 4 are applied to
the substrate 1 before a first structuring step subsequently takes place.
As shown in FIG. 3b, a separating line 30 is introduced into the
photoactive layer 3 and back side electrode 4 as the first structuring
step. As described in connection with the separating line 12 in FIG. 1,
the separating line 30 can be formed by radiation with laser light of
appropriate wavelength, for example 532 nm.

[0089]Then the contact line 31 shown in FIG. 3c is created. By radiation
with laser light of appropriate wavelength from a range of, for example,
200 nm to 10 μm, from the layer side the back side electrode 4 and
photoactive layer 3 are melted in a locally limited manner, but not
evaporated. It is likewise possible to direct the laser light from the
substrate side. In this case wavelengths of about 300 nm to 2 μm, for
example, are suitable.

[0090]Either a silicide, for example, AgAlSi with quasi-metallic
conductivity, or an eutectic of Si and Ag, which likewise has high
conductivity, forms due to diffusion processes in the melt. Because of
this, current can flow from the back side electrode 4 to the front side
electrode 2 at this place. Preferably, in the region of the contact line
31 there is ohmic contact to the front side electrode 2. The process for
formation of the contact line 31 is not restricted to the material system
indicated in the embodiment example. The mixture of elements from the
photoactive layer 3 and the back side electrode 4 in the locally formed
melt can also be used with other systems to form a conductive material
compound or alloy.

[0091]Then, to the left of separating line 31, a separating line 32 is
formed to interrupt the front side electrode 2. To form separating line
32 laser light at a wavelength that is absorbed in the front side
electrode 2, for example, 1064 nm, is introduced through the substrate 1.
The laser power and processing time are chosen so that the front side
electrode 2 becomes locally heated and stimulated to recrystallization
processes without the material being physically removed. In contrast to
the separating lines 20 and 21 described in connection with FIG. 2 or the
separating line 30 in this embodiment example, in the case of separating
line 32 material therefore is not removed, but rather only its properties
are changed, in particular, its conductivity. A gap is not formed. The
layers lying on top of the front side electrode 2, the photoactive layer
3 and the back side electrode 4 are not or are only negligently affected.
Here it is advantageous to use pulsed laser radiation, through which a
brief heating of the front side electrode 2 can be achieved locally
before the introduced amount of heat dissipates into the surroundings. In
this way a high temperature level can be briefly achieved locally without
the surroundings becoming significantly heated. Pulse durations that are
less than a microsecond and preferably that lie in the range of nano- or
picoseconds are especially suitable here. The change of microstructure of
the TCO material of the front side electrode 2 in the region of
separating line 32 caused by this leads to a clear decrease of its
conductivity in this region. The reason is that dopants are essentially
responsible for the conductivity of TCO layers and they are no longer
incorporated in the crystal as a consequence of the recrystallization
process. A second possible mechanism that leads to a drop of the
conductivity is achieved by mixing the material of the front side
electrode 2 with the material of the overlying photoactive layer sequence
3. The oxygen of the TCO material of the front side electrode 2 forms an
electrically isolating silicon oxide (SiO or SiO2) with the silicon
of the photoactive layer sequence 3. This operation is decisively
affected by the high enthalpy of oxide formation of silicon. Here it can
be advantageous to choose the parameters for the laser radiation
(wavelength, power, pulse duration) so that the photoactive layer
sequence 3 lying over the front side electrode 2 also becomes heated. It
is also conceivable to use laser radiation at two wavelengths at the same
time, one of which is preferably absorbed in the front side electrode 2
and the other is preferably absorbed in the photoactive layer sequence 3.
However, again no material is removed. The back side electrode 4 should
not be changed, so that the flow of current from the first segment 5
through contact region 6 into the second segment 7 at the right is not
adversely affected.

[0092]In both cases (separation of dopants; silicon oxide formation) the
front side electrode 2 is electrically interrupted or its conductivity is
sufficiently reduced. This process for formation of separating line 32 is
also not restricted to the material system indicated in the embodiment
example. For example, in the case of CI(G)S-based photoactive layer
sequences 3, Cu oxides, or in the case of photoactive layer sequences 3
that contain Cd, Cd oxides are formed in the separating line 32 and these
electrically interrupt the front side electrode 2 or sufficiently reduce
its conductivity in the region of separating line 32.

[0093]The result is shown in FIG. 3d, in which again the regions of a
first segment 5, a second segment 7 and the inbetween contact region 6
are represented and in which the flow of current in the series connection
of segments 5 and 7 is symbolized by arrows. The resulting thin layer
solar cell module is characterized by the silicon-containing contact line
31 in the back side electrode 4 and by the recrystallized or silicon
oxide-containing separating line 32 in the front side electrode 2.

[0094]As with the first embodiment example, here too it is advantageous
that all of the structuring steps be grouped together. In addition, at
least two of the structuring measures, namely the creation of separating
line 30 and contact line 31, which take place from the layer side, can be
implemented by a single process head. The remaining structuring measures,
the creation of separating line 32, can be implemented from the substrate
side with the thin layer solar cell module in the same position by a
second process head guided in parallel with the first process head. It is
especially advantageous that all of the layers are applied before the
group of structuring measures is carried out. To increase throughput in
structuring, moreover, a plurality of process heads can also be used in
parallel.

[0095]In an alternative embodiment of the process it is conceivable to
start with a substrate 1 that has already been provided with a TCO layer
as front side electrode 2 and in which the separating line 32 was already
created in a traditional way. In this case the photoactive layer sequence
3 and back side electrode 4 are therefore applied to a prestructured
front side electrode 2. Even though all of the structuring measures are
thus no longer combined together, this process offers an advantage over
the prior art, in which each layer deposition is followed by a subsequent
structuring measure.

[0097]As in the embodiment example shown in FIG. 3, first a front side
contact 2, a photoactive layer sequence 3 and a back side contact 4 are
applied to a substrate 1 (FIG. 4a). Then a separating line 40 is made in
the back side electrode 4 and the photoactive layer sequence 3 (FIG. 4b).
Then a contact line 41 is formed between the back side electrode 4 and
the photoactive layer sequence 3 is laterally spaced from separating line
40. Up to this process step the process runs exactly like the process
presented in connection with FIG. 3, for which reason one is referred to
the description given there for additional details.

[0098]Then, as represented in FIG. 4d, a separating line 42 is created,
which interrupts the entire layer structure except for the substrate,
thus the front side electrode 2, photoactive layer sequence 3 and back
side electrode 4. Separating line 42 can preferably be formed by
radiation of laser light of a suitable wavelength (1064 nm or 355 nm)
through the substrate. Alternatively, one can operate from the back side
using higher radiation energy. It is conceivable that all of the layers
are removed at the same time or that laser light of the same or different
wavelengths is used for radiation in steps that follow one another,
through which the layers are removed in a number of steps. For example,
in a first step, as in the formation of separating line 40, the
photoactive layer sequence 3 and a back side electrode 4 could be
removed, and in a second step, as in the formation of separating line 10
(see FIG. 1) or separating line 20 (see FIG. 2), the front side electrode
2 could be removed.

[0099]Finally, an electrically conductive adhesive strip 43 is applied
over separating line 42, due to which the undesired interruption of the
back side electrode 4 by separating line 42 is electrically reclosed. The
electrically conductive adhesive strip 43 can, for example, consist of a
conductive polymer. When applying it, care is to be taken that the
adhesive strip 43 not be laid over separating line 40, the purpose of
which is precise electrical separation of the back side electrodes 4 of
adjacent segments 5 and 7. The spacing of separating lines 40 and 42 is
about 100 μm. However, laying adhesive strip 43 with such positioning
precision is technical feasible. It is not necessary for the conductive
adhesive strip 43 to be applied over the entire width of the thin layer
solar cell module. It is enough if segments of the conductive adhesive
strip 43 that are distributed over the width are present as current
bridges.

[0100]The thin layer solar cell module that results from this production
process is depicted in FIG. 4e. Again the adjacent segments 5 and 7 and
the inbetween contact region 6 are entered and the current flow of series
connection of the segments is symbolized by arrows.

[0101]An alternative method for connecting the back side electrode 4 that
has been separated by separating line 42 is shown in FIG. 4f. Instead of
adhesive strip 43 a conductive strand 44 of a conductive paste is
applied; the consistency of the paste is chosen so that it does not or
only negligibly penetrates into separating line 42. The application of
the conductive paste, which can be a hardening conductive polymer, can
take place by ink jet printing technology. As in the case of the
conductive adhesive strip it is not necessary for the conductive strand
44 to be continuous over the width of the module, even though if there is
such a continuous embodiment better electrical connection and protective
sealing of separating line 42 are obtained as advantages.

[0102]The thin layer solar cell modules that result from these two process
alternatives are characterized by the silicide-containing contact line 41
and the adhesive strip 43 or adhesive strand 44 applied to the back side
electrode 4.

[0103]FIG. 5 shows a production line as a suitable apparatus for
conducting the production process for thin layer solar cell modules in
accordance with the application.

[0104]The production line has a first transport system 50 for acceptance
of a glass substrate 51. The transport system 50 leads into a cleaning
station 52, which is connected via a first vacuum lock 53 to a coating
device 54. The coating device 54 has a second transport system 55, a
first PVD/(LP)CVD coating station 56, a plurality of PECVD coating
stations 57 and a second PVD/(OP)CVD coating station 58. Connected to the
second PVD/(LP)CVD coating station 58 is a second vacuum lock 59, from
which a third transport system 60 emerges. This third transport system 60
leads to a structuring device 61, which has several movable process heads
62. After passing through the structuring device 61 on the third
transport system 60 a finished thin layer solar cell base module 63
leaves the production line.

[0105]The starting point of production of a thin layer solar cell module
in the presented production line is the glass substrate 51 which is
delivered by the first transport system 50. Preferably, the production
line is designed so that flat glass sheets of the conventional width of
3.21 m can be accommodated and processed. In the event the production
line can also preferably be directly coupled to a sheet glass production
line. After cleaning in cleaning station 52 the glass substrate 51 is
delivered directly to the first vacuum lock 53 without contact with the
surrounding atmosphere. For this reason one can omit a clean room
environment for protection against dust particles.

[0106]The electrode can be applied in the subsequent first PVD/(LP)CVD
coating station 56. In a CVD (chemical vapor deposition) coating a low
pressure process (LPCVD--low pressure CVD) can be used. In addition, a
(dry) etching device can be integrated into the first PVD/(LP)CVD coating
station 56. Preferably, the first PVD/(LP)CVD coating station 56 operates
in a continuous (in-line) process.

[0107]After that a photoactive layer sequence can be applied in the
different PECVD coating stations 57. Preferably, these PECVD coating
stations 57 are designed as stationary coating stations. Alternatively,
the electrode can also be applied in a stationary process in one of these
stations. In the event the first PVD/(LP)CVD coating station 56 could be
omitted. In addition, there is also the possibility that the glass
substrate 51 already has a front electrode, for example, due to on-line
coating in the glass manufacturer's production line. In the event the
first PVD/(LP)CVD coating station 56 could also be omitted. It is further
conceivable that if the front side electrodes are produced in a PVD
coating process a connected (dry) etching process is used for the
required roughening of the front electrode. The corresponding process
station is either integrated into the first PVD/(LP)CVD coating station
56 or into one of the PECVD coating stations 57. Because of the
arrangement of the coating stations 56, 57 and 58 an inexpensive linear
roller drive can serve as the second transport system 55 in the vacuum of
the coating plant 54.

[0108]To produce Si tandem cells, hydrogen-terminated amorphous p-, i- and
n-doped a-Si:H layers and/or microcrystalline p-, i- and n-doped Si
layers and/or other absorber layers based on a-Si(Ge):H can be applied in
succession by the PECVD coating stations 57. Moreover, the production
line is laid out so that the glass substrate passes through the second
PVD/(LP)CVD coating stations 58 after the PECVD coating stations 57
without breaking the vacuum, and the metal layer of a back side electrode
is applied, for example, in a sputtering process. Again the second
PVD/(LP)CVD coating station 58 is preferably laid out as an in-line
station for a continuous coating process and can operate in a low
pressure process in the case of a CVD coating. It is also conceivable for
there to be a plurality of second PVD/(LP)CVD coating stations 58 in
order to be able to deposit different metals, for example, Ag and/or Al
and/or Mo.

[0109]Then the glass substrate 51 is removed from the vacuum through the
second vacuum lock 59 and, on the third transport system 60, passes
through the structuring device 61 of the production line.

[0110]Correspondingly, the indicated production line can also be used to
produce thin layer solar cell modules based on compound semiconductors
(CdTe, CIS).

[0111]The processes described in connection with FIGS. 2-4 are
characterized by the fact that grouping into process steps for layer
deposition and process steps for structuring, i.e., for formation of the
separating, isolating, cover and contact lines, is possible. This is
reflected in the combining of the process stations needed for deposition
of the layers in the coating device 54 and the combining of the
structuring tools needed for structuring in the structuring device 61.
Lasers, laser transmission optics, ink jet printing heads and devices for
application of adhesive strips can be used as structuring tools. Here it
is advantageous to integrate as many as possible of the structuring tools
that are required for related process steps into one process head 62.
This applies, for example, to lasers of different wavelength, which
create different separating lines, ones which are to be positioned as
precisely correctly with respect to each other. In this connection one is
also directed to the remarks concerning FIGS. 2-4 with relevance to the
advantageous embodiments of the process heads. A plurality of identical
process heads 62, with which different parallel regions of a glass
substrate 51 can be processed, can be present in order to increase
throughput.

[0112]If application of the back side electrode 4 is still necessary after
the substrate has left the structuring device 61, for example, to produce
the thin layer solar cell module described in connection with FIG. 2, the
second PVD/(LP)CVD coating station 58 can optionally be separately
implemented instead of being integrated into the coating device 54. The
combining of the PECVD coating stations 57 and the first PVD/(LP)CVD
coating station 56 into the coating device 54 is not affected by this.

[0113]Then one has the finished thin layer solar cell base module 63.
Subsequently only peripheral processing steps like encapsulation,
stripping the edges, adding connections, etc., for the final preparation
of the thin layer solar cell module are necessary. These steps can be
carried out independently outside of the production line or can also be
integrated into the production line.